Overexpression of Grb2-associated binding protein 1 (GAB1) has been observed in several human cancers, such as breast and lung cancers. This protein is a substrate of several growth factors and interleukin receptors, and it is involved in the integration of different signal transductions. Particularly, GAB1 mediates the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI-3K) cascades. It belongs to a family of scaffolding proteins closely related to the insulin receptor substrates (e.g., IRS1). It contains an N-terminal pleckstrin homology (PH) domain binding to phosphatidylinositol-(3,4,5)-triphosphate (PtdIns(3,4,5)P3), tyrosine phosphorylation sites for the Src homology 2 (SH2) binding and a proline-rich domain interacting with Src homology 3 (SH3) domain. PH domains can be subdivided into four groups based on their selective binding to phosphoinositides, and GAB1 PH domain belongs to Group 1 which exhibits the strongest binding to PtdIns(3,4,5)P3, but weak affinity and specificity to PtdIns(3,4)P2 or PtdIns(4,5)P2. Additionally, the phosphorylation of GAB1 on Y627 depends on the intracellular translocation from cytosol to membrane by binding to PtdIns(3,4,5)P3 via its PH domain. Therefore, inhibition of GAB1 PH domain functions may prevent the recruitment of GAB1 to the membrane and suppress cancer cell (e.g., breast cancer) proliferation and metastasis. Herein, the inventors have identified novel small molecule inhibitors that selectively target the PH domain of GAB1, and that exhibit high therapeutic potency for cancer treatment.
Unfortunately, no three-dimensional (3D) structure is available to date for GAB1 PH domain or any PH domain in complex with drug-like small molecules. Challenges remain for accurate structural prediction due to its low sequence identity (<30%) to other PH domains with known structures. However, the core n-sandwich fold among PH domains is conserved, making it possible to construct a reliable homology model structure of GAB1 PH domain. Here, based on the position-site specific matrixes (PSSM) obtained from all non-redundant PH domain structures, the inventors performed fold recognition and homology modeling, followed by intensive structural refinement. The resulted model was then applied to high-throughput virtual screening of a unique collection of over five million drug and lead-like compounds with an in-house drug discovery workflow (FIG. 1). Upon biological evaluation, five out of the initially tested 20 hits exhibited positive activities to form direct binding to GAB1 PH domain, inhibit GAB1 Y627 phosphorylation and suppress breast cancer cell proliferation with low micromolar IC50. As is known, triple negative breast cancers are more aggressive with poor prognosis and difficult to treat clinically, but the inhibitors showed high potency against these malicious cells. Therefore, this present invention validates the effectiveness of the in silico platform for drug discovery, and demonstrates that targeting the PH domain of GAB1 provides a promising and novel therapeutic strategy for cancer treatment.
Outside of biological treatments, there are other ways to treat cancer. These include: surgery, chemotherapy, and radiation therapy. Surgery is usually only used in cancer that is isolated in one place and not metastasized cancer. Chemotherapy has ill side-effects due to it targeting many fast growing cells. Radiation therapy has the potential to kill even non harmful cells. Within biological treatments, there are four main categories. The first is rituximab, which can target antigens on cancerous cells which in turn can signal antigens on B-cells. These B-cells can then lyse the cancerous cells. One major advantage that the present invention has over these types of therapies is versatility. In order to target specific antigens, the drug must be specifically made to do this. Antigens differ from cell to cell, so different drugs have to be made to target different cell types.
Another type of treatment involves removing the immune system's inability to attack the body's own cells. Drugs such as ipillimumab can allow immune cells to attack body tissue. This opens up a large possibility of immune cells attacking tissue that is not cancerous or harmful. Therefore, a variety of autoimmune issues may emerge from this treatment path. A third type of biological cancer treatment involves attaching a cell-killing substance onto an antibody. When the antibody binds onto a cancerous cell antigen, the cancer cell with intake the cell-killing substance, and promptly undergoes cell death. Again, there is the chance that non-cancerous cells may uptake this substance and undergo apoptosis. Lastly, there exist the inhibitory biological compounds similar to the present invention. In addition to inhibiting GAB1 there are compounds which inhibit other molecules like growth effectors such as cetuximab and panitumumab. Unlike the present invention, these treatments are usually specific to cancer that is caused by a mutation in the KRAS gene.
In the present invention, the compounds may be used as a cancer therapeutic drug. Some advantages of the present invention are that the compound works upstream of other chemical components, the compounds do not directly target components of the immune system, and this biological inhibitor-based treatment has less damaging side effects than radiation or chemotherapy. There are a few call signaling pathways that are heavily involved in the pathogenesis of cancer. Two of these pathways are the RAS pathway and the PI3K pathway, and both of these pathways are deregulated in the formation of human cancer thereby leading to the over-production of GAB1. It has been shown that inhibiting upstream components of pathways complicit in tumorigenesis can reduce the rate of cancer. This is demonstrated in inhibitions of PI3K in the PI3K pathway. The invention has demonstrated that GAB1 inhibitors exist in a variety of compounds and that they have the potential to reduce the rate of tumorigenesis in humans.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.